Apparatus for controlling discharge lamps



Jan. 1, 1935. w. F.,WESTENDORP 1,986,514

APPARATUS FOR CONTROLLING DISCHARGE LAMPS I Original Filed June 7, 1933Inventor": Willem F Westendorp,

brg BMW IS Attorney,

Patented Jan. 1, 1935 UNITED STATES PATENT OFFICE Willem F. Westendorp,Schenectady, N. Y., assignor to General Electric Company, a corporationof New York Application June 7, 1933, Serial No. 674,698 RenewedSeptember 18, 1934,

8 Claims.

My invention relates to apparatus for controlling electric dischargelamps operated on polyphase alternating current circuits. It relatesparticularly to apparatus for varying the illumination of dischargelamps having the form of long, narrow tubes, sometimes termed positivecolumn lamps, which because of the large ratio of their length to theirdiameter will not start operating merely with the application of avoltage which is sufficiently high to keep them operating after theyhave been started. Where such lamps are operated by alternating currentit is necessary to restart them at each half cycle upon which theyoperate.

One object of my invention is the provision of improved apparatus forstarting electric discharge lamps operated on polyphase circuits.Another object is the provision of improved apparatus for varying atwill the amount of illumination produced by such lamps when operated onpolyphase circuits. v

Y My invention will be better understood from the following descriptiontaken in connection with the accompanying drawing, and its scope will bepointed out in the appended claims.

Referring to the drawing, Fig. 1 is a circuit diagram illustrating oneembodiment of my invention; and Fig. 2 shows a series of curves toillustrate the operation of the apparatus shown in Fig. 1.

In Fig. 1, reference number 5 represents a polyphase alternating currentsource of supply, which for example may be 120-volt, 60-cycle, and whichin the present case is shown as three phase, the phase conductorsthereof being represented by the letters A, B, and C. Connected betweenthe respective phase conductors and neutral, which is represented by theletter N, are the three similar electric discharge lamps 6, 7, and 8,whereby each lamp is operated on a separate phase of the alternatingcurrent supply. The lamps are of the positive column type eachcomprising a tubular envelope of transparent material such as glass orquartz, having a cathode 9, which-may be a hot or a cold cathode butpreferably is a hot cathode, in an enlargement or bulb at the lower endofthe lamp and an anode 10 at the opposite end. The cathode 9, if a. hotcathode, may be provided with a heater of well-known form which is notshown, nor is the heating circuit thereof shown. An example of a coldcathode is the well-known mercury cathode. Depending upon the characterof the light desired from the lamp, the envelope after having beenevacuated is supplied with a metal vapor such as sodium vapor or mercuryvapor or with a gas such as neon, krypton, etc., or with a mixture of agas and a vapor, all being under low pressure. Inasmuch as a lamp ofthis character has a negative volt-ampere characteristic a suitableimpedance must be used in circuit with the lamp to hold the currenttaken thereby within safe limits. For this purpose I have shown thereactor 11 connected in series with the anode of each lamp. This reactorhas in addition to the usual winding thereof the auxiliary winding 12comprising a few turns of wire wound on the same core as the mainwindingand thereby comprising in effect a transformer whose purpose isto induce a voltage impulse in the main winding of the reactor to causethe lamp to start as will be explained later.

As mentioned above, a discharge lamp of the type illustrated will notstart of its own accord merely by connecting it with the source ofcurrent supply 5, but if it is started in each positive half cycle,namely, the half cycle in which its anode is positive with respectto itscathode, it will continue to operate through the remainder of each ofthose half cycles. In order to start the lamp in each positive halfcycle I cause a voltage impulse to be applied to the lamp in each ofthose half cycles, which impulse added to the voltage of the supplycircuit is sufficient to start a discharge in the lamp. The means whichI have devised for applying the voltage impulsesfor starting the lampcomprises the capacitor 14 arranged in series with the auxiliary winding12 and connected through the rectifier 15 and controlling resistor 16with a suitable source of voltage. Certain broad aspects of my inventionfor so starting discharge lamps are disclosed and claimed in my PatentNo. 1,976,645, Oct. 9, 1934.

In accordance .with my present invention the source of voltage forcharging the capacitor 14 is the three phase step-up transformer 17 theprimary of which is connected with the polyphase source 5 and which, forexample, may be wound for volts while the secondary may be. wound for1500 volts. The capacitor 14, associated with lamp 8 which is connectedwith phase C, is supplied with voltage through rectifier 15 notfromphase C of transformer 17 but with reversed phase A of that transformer,the reversal of the phase being indicated by showing the neutralconnection of the secondary at the opposite end from the neutralconnection of the primary. The capacitor 14 thus charged from 5 reversedphase A of transformer 17 is allowed quickly to discharge at the properinstant through the auxiliary winding 12, the discharge circuitincluding the resistor 18 and the control device or valve 19. Thisdevice preferably is a, vapor electric discharge device and is shownhaving an anode20, a control grid 21 and a hot cathode 22.When'device'19 begins to conduct current by the application of theproper voltage to its grid the relatively large discharge current fromthe capacitor passing through the winding 12 induces a voltage in themain reactor winding which is sufiicient to cause the lamp to start. Theinstant at which the vapor device allows the capacitor to dischargethrough winding 12 is determined by the phase controlling apparatus nowto be described.

This apparatus is shown as comprising a stator 25 having a three phasedistributed winding which is connected with the polyphase source ofsupply 5. Inductively related with this winding is the rotor 26 whichalso has a three phase distributed winding, which is shown connectedwith a three phase load device 27 comprising the three resistors 28.These resistors are shown as Y-connected, the neutral being connectedwith the neutral N and the opposite ends of the resistors beingconnected through resistors 29 with the grid circuits of the vaporelectric devices 19. Since the rotating magnetic field produced by thestator 25 induces a three phase voltage in the winding 26 cf the rotorthe voltages applied to the grids of the vapor devices 19 will be threephase and of the same frequency as that of the source 5, and will .besimilarly related to the anode voltages of said devices. By angularlyadjusting the rotor with respect to the statorthe phase of the voltageapplied to the grid of each device 19 may be delayed or advanced withrespect to the phase of the anode voltage thereof. Hence the instant ofstarting of the discharge lamps can be varied at will throughout thehalf -cycle upon which they operate thereby causing pose I have providedthe rotor 26 with the shaft 30 upon which is mounted the crank 31arranged to engage the cam 32. The torque produced between the rotor andstator is suflicient to hold the arm 31 in engagement with the cam. Fordriving the cam I have shown the clock 33 which in rotating the camcauses the rotor to oscillate slowly back and forth through thenecessary angle to give the proper phase adjustment and therebyperiodically to vary the illumination.

While I have described the above apparatus with special reference tothat associated directly with lamp 8, which is operated on phase C, itis to be understood that a similar apparatus is associated with each ofthe other lamps 6 and 7, which are operated on phases A and Brespectively, the only difference being that the charging circuit forthe capacitor associated with lamp 7 is connected with reversed phase C,indicated by C, and the charging circuit for the capacitor associatedwith lamp 6 .is connected with reversed phase B indicated by B.

To assist in the clear understanding of the operation of theabove-described apparatus I have shown a series of waves in Fig. 2representing the various phase relations existing in age the capacitor14 associated with lamp 8 during the charging of this capacitor fromreversed phase A. Curve 37 represents the voltage applied to the grid ofvapor device 19 associated with lamp 8 produced by the phase controllingapparatus. At the point where this grid voltage becomes positive thevapor device immediately begins to conduct current and therefore toallow the capacitor suddenly to discharge through winding 12 and hencestart lamp 8. The vertical line 38 represents the condenser dischargeand also the instant at which the lamp begins to operate. The lamphaving thus been started continues to operate through the remainder ofthat half cycle, that part of the half cycle through which the lampoperates being indicated by the hatching. It will thus be seenthat bymaking use of the reversed A phase to charge the capacitor a fulldischarge is available at the instant at which the lamp is to-bestarted. In a similar manner the capacitor associated with lamp 6, whichis on phase A, is charged from reversed phase B and is discharged by theoperation of the vapor device associated therewith. Also the capacitorassociated with lamp '7, which is on phase B, is charged from reversedphase C and is discharged at the proper instant by the vapor deviceassociated therewith. As the rotor 26 of the phase controlling apparatusis adjusted to delay the grid voltage 37 of device 19, the instant atwhich the lamp 8 is started is correspondingly delayed in each positivehalf cycle. Finally when the grid voltage 37 reaches a delayed positioncorresponding to that indicated by the dotted line 40 the operatingvoltage applied to the lamp has reached a value too low to maintain adischarge and hence the lamp does not start. The capacitor, however,does discharge each time the vapor device is tripped and the impulsevoltage produced in the reactor of the lamp produces a weak flash oflight in the lamp. It will be noted however that when the grid voltagehas reached a still further delayed position than that represented by 40where the lamp should be entirely dark the tripping of the vapor deviceoccurs at the beginning of the next positive half cycle of reversedphase A. The current which would charge the capacitor from reversedphase A now is free to pass through the vapor device and since thecondenser receives only that small charge corresponding withthepotential drop across resistor 18 and the vapor device no suddendischarge takes place; hence the lamp remains totally dark at thosetimes at which illumination is not desired.

and scope of my invention which modifications I aim to cover by theappended claims.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. In combination, a source of polyphase alternating current supply, anelectric discharge lamp connected to operate on one phase thereof, andmeans energized by another phase thereof for inducing a starting voltagein the circuit of said lamp.

2. In combination, a source of polyphase alternating current supply, anelectric discharge lamp connected with one phasethereof, means forreversing another phase thereof, energy storing means connectedtherewith and means for causing the energy stored in the storing meansto produce a starting voltage in said lamp.

3. In combination, a source of polyphase alternating current supply, anelectric discharge lamp connected with one phase thereof, a reactor insaid connection, means for reversing another phase of said supply, acapacitor arranged to be charged from said reversed phase and means forcausing the energy stored in said capacitor to induce a starting voltagein said lamp.

4. In combination, a source of po yphase alternating current supply, anelectric discharge lamp connected with one phase thereof, a reactor insaid connection having an auxiliary winding, means for reversing anotherphase of said supply, a capacitor arranged to be charged from saidreversed phase, and means for discharging said capacitor through saidauxiliary winding.

5. Incombination, a source of polyphase alternating'current supply, anelectric discharge lamp connected with one-phase thereof, means forreversing another phase thereof, means energized by said reversed phasefor supplying a starting voltage to said lamp, and means for varying thepoint on the wave of said one phase at which said starting voltage isproduced.

6. In combination, a source of polyphase alternating current supply.anelectric discharge lamp connected with one phase thereof, a reactor insaid connection, means for reversing another phase of said supply, acapacitor arranged to be charged from said reversed phase, means forcausing the energy stored in said capacitor to induce a starting voltagein said lamp, and phase controlling apparatus for varying the point onthe wave of said one phase at which said energy induces said startingvoltage.

7. In combination, a source of polyphase alternating current supply, anelectric discharge lamp connected with one phase thereof, a reactor insaid connection having an auxiliary winding,

means for reversing another phase of said sup-- ply, a capacitorarranged to be charged from said reversed phase, means for dischargingsaid capacitor through said auxiliary winding comprising a gridcontrolled vapor electric discharge device and phase controllingapparatus connected with the grid circuit of said device.

8. In combination, a source of polyphase alternating current supply, anelectric discharge lamp CERTIFICATE or CORRECTION Patent No. 1,986,614.'January I, 1935.

WILLEM F. WESTENDORP.

It is hereby certified that error appears in the printed specificationof the above numbered patent requiring correction as follows: Page 2,second column, line 27, for "discharge" read charge; and that the saidLetters Patent should be read with this correction therein that the samemay conform to the record of the case in the Patent Office. v

Signed and sealed this 12th day of March, A. D. 1935.

Leslie Frazer Acting Commissioner of Patents.

